Known hypersensitivity or allergy to linagliptin or its excipients or metformin or placebo

Treatment with anti-obesity drugs 3 months prior to informed consent or any other treatment at the time of screening

Alcohol or drug abuse within the 3 months prior to informed consent that would interfere with trial participation or any ongoing condition leading to a decreased compliance to study procedures or study drug intake in the opinion of the investigator.

Concurrent participation in another clinical trial or any investigational therapy within thirty days prior to signing the consent form or during the trial.

Pre-menopausal women (last menstruation </= 1 year prior to informed consent) who are nursing or pregnant or are of child-bearing potential and are not practicing an acceptable method of birth control, or do not plan to continue using this method throughout the study

Current treatment with systemic steroids at time of informed consent or change in dosage of thyroid hormones within 6 weeks prior to informed consent.